The invention relates to an injection system for injecting liquids within a strong magnetic field, an alternating magnetic field and/or a high-frequency electric field, for use with a medical technical system, comprising a room which is shielded from electromagnetic fields by means of a shield, an injection device, by means of which liquid to be injected can be dispensed to a patient, a drive device of the injection device, by means of which at least one conveying element can be displaced, and a control and monitoring unit which is arranged outside the room.
Such injection systems are used in particular in the field of magnetic resonance imaging (MRI), in order by injection of a contrast agent to obtain tomograms of internal organs of a patient that allow diagnosis. It is generally known that MRI systems have to be isolated in the best possible way from external electromagnetic fields, so as to obtain an optimal image quality or tomogram quality using the MRI system. This is achieved by shielding from such (sometimes unpredictable) sources of electromagnetic fields the entire room in which the MRI system is located, by means of a copper shield or by means of conductive mesh material. In order to take full advantage of such a shielded room, attempts are also made to shield from the MRI system the injection system and method for injecting liquids, in particular contrast media and saline solution for use with an MRI system, or to move at least part of said system and method outside, since the injection system and method may themselves be sources of electromagnetic fields and may have an adverse effect on image quality.
An injection system of the type described in the introduction is known in general for example from U.S. Pat. No. 5,494,036 A. By extensive design measures, this system prevents the image quality from being too greatly affected by electromagnetic radiation.
The injection device disclosed in U.S. Pat. No. 5,494,036 A consists of a drive device in the form of two DC electric motors and two cylinder/piston units in the form of syringes. Via a coupling device, which may optionally also be configured in a hydraulic manner but in particular is formed by two drive spindles (flexible drive shaft), the pistons of the syringes are moved forwards and backwards independently of one another by means of the drive spindles. Here, a rotational movement of a threaded and axially fixed drive element of the respective electric motor is converted into a linear forward and backward movement of the piston in the syringe. As a result of the forward and backward movement of the syringe piston, contrast agent and saline solution can be taken up and subsequently dispensed. The syringes can be connected via a Y-shaped adapter and intermediate hoses to a catheter, through which the contrast agent and the saline solution can be injected into the patient during the imaging process.
The electric motors are connected via shielded electric cables to a battery which is located inside the room. The electric motors are in particular controlled by an injection monitoring unit arranged in the room, which is connected to a transmitting and receiving device located in the shielded room. The superior control and monitoring unit is connected to a further transmitting and receiving device located outside the room. Via the two transmitting and receiving devices, the control and monitoring unit controls and monitors the injection monitoring unit.
One disadvantage of such a system is that, due to the battery, the transmitting and receiving device and in particular the two electric motors and the injection monitoring unit, possible sources of electromagnetic fields are present which could reduce the quality of the MRI image. In order to avoid these potential sources of interference, therefore, electrically non-conductive materials are used and complicated shielding of all the aforementioned objects and their supply lines and connecting lines is carried out. Moreover, for the reasons mentioned above, a sufficient minimum distance of the objects from the magnet must be maintained at all times during the imaging process, which is associated with a certain risk of imperfect images in the event of the specialist personnel inadvertently not providing this minimum distance. Another disadvantage is the weight of the objects, in particular of the battery, and the space requirement thereof. In view of the high costs of shielding the room, the space required for the known system is very expensive. Finally, another disadvantage is the fact that rapid and unhindered access to the patient and/or magnet in the known system is made difficult due to the presence of tripod or carriage structures on which the known system is partially installed, and due to cables running across the floor.